Nineteen children are among the dead after a round of airstrikes by the Syrian government on a rebel enclave near Damascus.

The town of Douma in Eastern Ghouta was under siege on Wednesday, with the Syrian Observatory for Human Rights reporting that 34 people had been killed and about 200 more injured in the bombardment.

It came less than 24 hours after the region - controlled by rebel factions, including Islamists - suffered some of its worst bloodshed in years, with 80 civilians left dead by regime warplanes.

Image:A man makes his way through the rubble after the Syrian government's latest round of airstrikes

Rami Abdel Rahman, director of the UK-based observatory, said Tuesday had seen "the highest civilian toll in Syria in nearly nine months, and one of the bloodiest days in Eastern Ghouta for several years".

Beit Sewa and Hammuriyeh, two small towns in the district, were the hardest hit, with some of the munitions thought to contain chlorine.

The global chemical weapons watchdog, the Organisation for the Prohibition of Chemical Weapons, expressed "grave concern" over the "credible allegations".

"Eastern Ghouta is a de-escalation area. If anything, there has been a serious escalation. The conflict in Syria is far from over. It's the first time - between Eastern Ghouta, Idlib, Afrin - we have multiple fronts with people in extreme danger without a view to a solution."

Image:About 200 people are thought to have been injured

More than 340,000 people have been killed and millions displaced since the conflict in Syria erupted in March 2011.